U.S. patent application number 13/257991 was filed with the patent office on 2012-02-16 for wavelength division multiplexer compatible with two types of passive optical networks.
This patent application is currently assigned to ZTE CORPORATION. Invention is credited to Dan Geng, Jie Su, Songlin Zhu.
Application Number | 20120039605 13/257991 |
Document ID | / |
Family ID | 42997869 |
Filed Date | 2012-02-16 |
United States Patent
Application |
20120039605 |
Kind Code |
A1 |
Zhu; Songlin ; et
al. |
February 16, 2012 |
Wavelength Division Multiplexer Compatible with Two Types of
Passive Optical Networks
Abstract
A wavelength division multiplexer is provided by the present
invention, which implements the wavelength division multiplexing
and de-multiplexing of the optical signals in the basic and upgrade
bands by reasonably arranging the filters and selecting the
spectral properties of the filters, so that the existing time
division multiplexing passive optical network (TDM-PON) can
transmit the next generation passive optical network (NG-PON)
simultaneously and the existing TDM-PON can be smoothly upgraded to
the NG-PON, meanwhile, it provides the deployed TDM-PON with the
subsequent network compatibility. The wavelength division
multiplexer provided in the present invention can meet the high
isolation requirement of the optical signals in working band with
low cost, and takes both the isolation requirement and the optical
network insertion loss requirement into account, thus it has high
reliability, is easy to use and for system upgrade.
Inventors: |
Zhu; Songlin; (Guangdong
Province, CN) ; Geng; Dan; (Guangdong Province,
CN) ; Su; Jie; (Guangdong Province, CN) |
Assignee: |
ZTE CORPORATION
Shenzhen City, Guangdong Province
CN
|
Family ID: |
42997869 |
Appl. No.: |
13/257991 |
Filed: |
September 24, 2009 |
PCT Filed: |
September 24, 2009 |
PCT NO: |
PCT/CN2009/074200 |
371 Date: |
October 18, 2011 |
Current U.S.
Class: |
398/58 |
Current CPC
Class: |
H04J 14/0226 20130101;
H04J 14/0246 20130101; H04J 14/0201 20130101; H04J 14/0252
20130101; H04J 14/0282 20130101; H04J 14/0247 20130101; H04J 14/025
20130101; H04J 14/0232 20130101; H04J 14/02 20130101 |
Class at
Publication: |
398/58 |
International
Class: |
H04J 14/02 20060101
H04J014/02 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 21, 2009 |
CN |
200910135534.4 |
Claims
1. A wavelength division multiplexer compatible with two passive
optical networks, comprising an upgrade optical line terminal port,
a legacy optical line terminal port, a common port, and one or more
filters, wherein, said one or more filters are configured: in a
downlink direction, to multiplex an optical signal in a basic band
input from the legacy optical line terminal port and an optical
signal in an upgrade band input from the upgrade optical line
terminal port, and to output the multiplexed optical signal via the
common port; in an uplink direction, to de-multiplex a wavelength
division multiplexed optical signal input from the common port into
the optical signal in the basic band and that in the upgrade band
respectively, and to output the optical signal in the basic band
via the legacy optical line terminal port and the optical signal in
the upgrade band via the upgrade optical line terminal port; both
said basic band and upgrade band comprise the downlink band
transmitted in the downlink direction and the uplink band
transmitted in the uplink direction; therefore, compatibility of a
next generation passive optical network which uses the upgrade band
and an existing time division multiplexing passive optical network
which uses the basic band can be achieved.
2. A wavelength division multiplexer of claim 1, wherein, said
wavelength division multiplexer comprises a plurality of filters,
and said filters are configured as that: there is at least one
filter among said a plurality of filters whose transmission band
comprises the uplink band in the basic band and reflection band
comprises the uplink band in the upgrade band in an uplink optical
channel from a filter de-multiplexing optical signals in the uplink
band in the basic band and in the uplink band in the upgrade band
to the legacy optical line terminal port; there is at least one
filter among said a plurality of filters whose transmission band
comprises the uplink band in the upgrade band and the reflection
band comprises the uplink band in the basic band in an uplink
optical channel from the filter de-multiplexing optical signals in
the uplink band in the basic band and in the uplink band in the
upgrade band to the upgrade optical line terminal port; there is at
least one filter among said a plurality of filters whose
transmission band comprises the downlink band in the basic band and
reflection band comprises a downlink band in the upgrade band in a
downlink optical channel from the legacy optical line terminal port
to a filter multiplexing optical signals in the downlink band in
the basic band and the downlink band in the upgrade band; and there
is at least one filter among said a plurality of filters whose
transmission band comprises the downlink band in the upgrade band
and reflection band comprises the downlink band in the basic band
in a downlink optical channel from the upgrade optical line
terminal port to the filter multiplexing optical signals in the
downlink band in the basic band and the downlink band in the
upgrade band.
3. A wavelength division multiplexer of claim 2, wherein any of
said a plurality of filters comprises a transmission port, a
reflection port and a common port, or comprises a transmission port
and a common port, said reflection port and common port being at
one side of said filter, while said transmission port being at the
other side other than the side in which said reflection port and
common port locate; said wavelength division multiplexer comprises
a first filter, a second filter, a third filter and a fourth
filter, and is configured as that: there are optical channels
between the upgrade optical line terminal port and the common port
of the first filter, between the reflection port of the first
filter and the transmission port or the common port of the fourth
filter, between the common port or the transmission port of the
fourth filter and the reflection port of the third filter, between
the transmission port of the first filter and the reflection port
of the second filter, between the legacy optical line terminal port
and the transmission port of the second filter, between the common
port of the second filter and the transmission port of the third
filter, and between the common port of said wavelength division
multiplexer and the common port of the third filter.
4. A wavelength division multiplexer of claim 3, wherein, said
first filter is a band-pass or sideband filter, and the
transmission band of said first filter comprises the downlink band
in the upgrade band and the reflection band of said first filter
comprises the basic band and the uplink band in the upgrade band;
said second filter is a sideband filter, and the transmission band
of the second filter comprises the basic band and the uplink band
in the upgrade band, and the reflection band of said second filter
comprises the downlink band in the upgrade band; said third filter
is a sideband filter, and the transmission band of said third
filter comprises the downlink band in the upgrade band and the
basic band, and the reflection band of said third filter comprises
the uplink band in the upgrade band; said fourth filter is a
band-pass or sideband filter, and the transmission band of the
fourth filter comprises the uplink band in the upgrade band, and
the reflection band of the fourth filter comprises the downlink
band in the upgrade band and the basic band; alternatively said
first filter is a band-pass or sideband filter, and the
transmission band of said first filter comprises the uplink band in
the upgrade band, the reflection band of said first filter
comprises the downlink band in the upgrade band and the basic band;
said second filter is a sideband filter, and the transmission band
of said second filter comprises the downlink band in the upgrade
band and the basic band, the reflection band of said second filter
comprises the uplink band in the upgrade band; said third filter is
a sideband filter, and the transmission band of the third filter
comprises the uplink band in the upgrade band and the basic band,
the reflection band of the third filter comprises the downlink band
in the upgrade band; said fourth filter is a band-pass or sideband
filter, and the transmission band of the fourth filter comprises
the downlink band in the upgrade band, the reflection band of the
fourth filter comprises the basic band and the uplink band in the
upgrade band.
5. A wavelength division multiplexer of claim 2, wherein, any of
said a plurality of filters comprises a transmission port, a
reflection port and a common port, or comprises a transmission port
and a common port, said reflection port and common port are at one
side of said filter, while said transmission port being at the
other side other than the side in which said reflection port and
common port locate; said wavelength division multiplexer comprises
a first filter, a second filter, a third filter and a fourth
filter, and the wavelength division multiplexer is configured as
that: there are optical channels between the upgrade optical line
terminal port and the common port of the first filter, between the
reflection port of the first filter and the transmission port of
the third filter, between the transmission port of the first filter
and the reflection port of the second filter, between the
transmission port of the second filter and the transmission port or
the common port of the fourth filter, between the common port of
the second filter and the reflection port of the third filter,
between the common port of the third filter and the common port of
said wavelength division multiplexer, and between the common port
or the transmission port of said fourth filter and the legacy
optical line terminal port.
6. A wavelength division multiplexer of claim 5, wherein, said
first filter is a band-pass or sideband filter, and the
transmission band of the first filter comprises the downlink band
in the upgrade band, the reflection band of the first filter
comprises the uplink band in the upgrade band and the basic band;
said second filter is a sideband filter, and the transmission band
of said second filter comprises the uplink band of the upgrade band
and the basic band, the reflection band of said second filter
comprises the downlink band in the upgrade band; said third filter
is a band-pass or sideband filter, and the transmission band of the
third filter comprises the uplink band in the upgrade band, the
reflection band of the third filter comprises the downlink band in
the upgrade band and the basic band; said fourth filter is a
sideband filter, and the transmission band of the fourth filter
comprises the downlink band in the upgrade band and the basic band,
the reflection band of the fourth filter comprises the uplink band
in the upgrade band; alternatively said first filter is a band-pass
or sideband filter, and the transmission band of the first filter
comprises the uplink band in the upgrade band, the reflection band
of the first filter comprises the downlink band in the upgrade band
and the basic band; said second filter is a sideband filter, and
the transmission band of the second filter comprises the downlink
band in the upgrade band and the basic band, the reflection band of
the second filter comprises the uplink band in the upgrade band;
said third filter is a band-pass or sideband filter, and the
transmission band of the third filter comprises the downlink band
in the upgrade band, the reflection band of the third filter
comprises the uplink band in the upgrade band and the basic band;
said fourth filter is a sideband filter, and the transmission band
of the fourth filter comprises the uplink band in the upgrade band
and the basic band, the reflection band of the fourth filter
comprises the downlink band in the upgrade band.
7. A wavelength division multiplexer of claim 2, wherein, any of
said a plurality of filters comprises a transmission port, a
reflection port and a common port, or comprises a transmission port
and a common port, said reflection port and common port being at
one side of said filter, while said transmission port being at the
other side other than the side in which said reflection port and
common port locate; said wavelength division multiplexer comprises
a first filter, a second filter, a third filter and a fourth
filter, and is configured as that: there are optical channels
between the upgrade optical line terminal port and the common port
of the first filter, between the reflection port of the first
filter and the transmission port or the common port of the second
filter, between the transmission port of the first filter and the
reflection port of the fourth filter, between the common port or
the transmission port of the second filter and the reflection port
of the third filter, between the common port of the third filter
and the transmission port of the fourth filter, between the
transmission port of the third filter and the legacy optical line
terminal port, and between the common port of the fourth filter and
the common port of said wavelength division multiplexer.
8. A wavelength division multiplexer of claim 7, wherein, said
first filter is a band-pass or sideband filter, and the
transmission band of the first filter comprises the uplink band in
the upgrade band, the reflection band of the first filter comprises
the downlink band in the upgrade band and the basic band; said
second filter is a band-pass or sideband filter, and the
transmission band of the second filter comprises the downlink band
in the upgrade band, the reflection band of the second filter
comprises the uplink band in the upgrade band and the basic band;
said third filter is a band-pass or sideband filter, and the
transmission band of the third filter comprises the uplink band in
the upgrade band and the basic band, the reflection band of the
third filter comprises the downlink band in the upgrade band; said
fourth filter is a sideband filter, and the transmission band of
the fourth filter comprises the downlink band in the upgrade band
and the basic band, the reflection band of the fourth filter
comprises the uplink band in the upgrade band; alternatively said
first filter is a band-pass or sideband filter, and the
transmission band of the first filter comprises the downlink band
in the upgrade band, the reflection band of the first filter
comprises the uplink band in the upgrade band and the basic band;
said second filter is a band-pass or sideband filter, and the
transmission band of the second filter comprises the uplink band in
the upgrade band, the reflection band of the second filter
comprises the downlink band in the upgrade band and the basic band;
said third filter is an sideband filter, and the transmission band
of the third filter comprises the downlink band in the upgrade band
and the basic band, the reflection band of the third filter
comprises the uplink band in the upgrade band; said fourth filter
is a sideband filter, and the transmission band of the fourth
filter comprises the uplink band in the upgrade band and the basic
band, the reflection band of the fourth filter comprises the
downlink band in the upgrade band.
9. A wavelength division multiplexer of claim 1, wherein, said
wavelength division multiplexer comprises a filter, and said filter
is a band-pass filter, and there are optical channels between a
transmission port of the band-pass filter and the legacy optical
line terminal port, between a common port of the band-pass filter
and the common port of said wavelength division multiplexer, and
between a reflection port of the band-pass filter and the upgrade
optical line terminal port; and a transmission band of the
band-pass filter comprises the basic band, and a reflection band of
the band-pass filter comprises the upgrade band; alternatively
there are optical channels between the transmission port of the
band-pass filter and the upgrade optical line terminal port,
between the common port of the filter and the common port of said
wavelength division multiplexer, and between the reflection port of
the filter and the legacy optical line terminal port, and the
transmission band of the band-pass filter comprises the upgrade
band and the reflection band of the band-pass filter comprises the
basic band.
10. A wavelength division multiplexer of claim 2, wherein,
composition of a plurality of filters of the wavelength division
multiplexer and spectral properties of the filters are in one of
the following modes: mode 1: said wavelength division multiplexer
comprises a first filter, a second filter and a third filter, the
transmission band of the first filter comprises the downlink band
in the upgrade band, and the reflection band of the first filter
comprises the uplink band in the upgrade band and the basic band;
the transmission band of the second filter comprises the uplink
band in the upgrade band, and the reflection band of the second
filter comprises the downlink band in the upgrade band and the
basic band; the transmission band of the third filter comprises the
basic band, and the reflection band of the third filter comprises
the upgrade band; in connection, there are optical channels between
the upgrade optical line terminal port and a common port of the
first filter, between a reflection port of the first filter and a
transmission port of the second filter, between a transmission port
of the first filter and a reflection port of the second filter,
between a common port of the second filter and a reflection port of
the third filter, between a transmission port of the third filter
and the legacy optical line terminal port, and between a common
port of the third filter and a common port of said wavelength
division multiplexer; mode 2: positions of the first filter and the
second filter in mode 1 are exchanged, and the spectral property of
each filter is the same as that in mode 1; mode 3: said wavelength
division multiplexer comprises a fifth filter and a sixth filter, a
transmission band of the fifth filter comprises the basic band and
a reflection band of the fifth filter comprises the upgrade band; a
transmission band of the sixth filter comprises the upgrade band
and the reflection band of the sixth filter comprises the basic
band; in connection, there are optical channels between the legacy
optical line terminal port and the transmission port of the fifth
filter, between a common port of the wavelength division
multiplexer and a common port of the fifth filter, between the
upgrade optical line terminal port and a transmission port or a
common port of the sixth filter, and between the common port or the
transmission port of the sixth filter and a reflection port of the
fifth filter; mode 4, said wavelength division multiplexer
comprises a seventh filter and a eighth filter, a transmission band
of the seventh filter comprises the upgrade band and a reflection
band of the seventh filter comprises the basic band; a transmission
band of the eighth filter comprises the basic band and a reflection
band of the eighth filter comprises the upgrade band; in
connection, there are optical channels between a transmission port
of the seventh filter and the upgrade optical line terminal port,
between a reflection port of the seventh filter and a transmission
port or a common port of the eighth filter, between a common port
of the seventh filter and a common port of said wavelength division
multiplexer, and between the common port or the transmission port
of the eighth filter and the legacy optical line terminal port;
mode 5: said wavelength division multiplexer comprises a ninth
filter, a tenth filter and an eleventh filter, a transmission band
of the ninth filter comprises the upgrade band and a reflection
band of the ninth filter comprises the basic band; a transmission
band of the tenth filter comprises the uplink band in the upgrade
band and the basic band and a reflection band of the tenth filter
comprises the downlink band in the upgrade band; a transmission
band of the eleventh filter comprises the downlink band in the
upgrade band and the basic band and a reflection band of the
eleventh filter comprises the uplink band in the upgrade band; in
connection, there are optical channels between a transmission port
of the ninth filter and the upgrade optical line terminal port,
between a common port of the ninth filter and a common port of said
wavelength division multiplexer, between a reflection port of the
ninth filter and a common port or a transmission port of the tenth
filter, between the transmission port or the common port of the
tenth filter and the common port or the transmission port of the
ninth filter, and between the transmission port or the common port
of the ninth filter and the legacy optical line terminal port; mode
6: positions of the tenth filter and the eleventh filter in mode 5
are exchanged, and the spectral property of each filter is the same
as that in mode 5.
11. A wavelength division multiplexer of claim 1, wherein, the
filters in said wavelength division multiplexer are thin film
filters, and the uplink band in said upgrade band is 1260
nm.about.1280 nm, and the downlink band in said uplink band is 1550
nm.about.1580 nm; the uplink band in said basic band is 1290
nm.about.1330 nm, that is, a O band, and the downlink band in said
basic band is 1480 nm.about.1500 nm, that is, a S band.
12. (canceled)
13. A wavelength division multiplexer of claim 2, wherein, the
filters in said wavelength division multiplexer are thin film
filters, and the uplink band in said upgrade band is 1260
nm.about.1280 nm, and the downlink band in said uplink band is 1550
nm.about.1580 nm; the uplink band in said basic band is 1290
nm.about.1330 nm, that is, a O band, and the downlink band in said
basic band is 1480 nm.about.1500 nm, that is, a S band.
14. A wavelength division multiplexer of claim 3, wherein, the
filters in said wavelength division multiplexer are thin film
filters, and the uplink band in said upgrade band is 1260
nm.about.1280 nm, and the downlink band in said uplink band is 1550
nm.about.1580 nm; the uplink band in said basic band is 1290
nm.about.1330 nm, that is, a O band, and the downlink band in said
basic band is 1480 nm.about.1500 nm, that is, a S band.
15. A wavelength division multiplexer of claim 4, wherein, the
filters in said wavelength division multiplexer are thin film
filters, and the uplink band in said upgrade band is 1260
nm.about.1280 nm, and the downlink band in said uplink band is 1550
nm.about.1580 nm; the uplink band in said basic band is 1290
nm.about.1330 nm, that is, a O band, and the downlink band in said
basic band is 1480 nm.about.1500 nm, that is, a S band.
16. A wavelength division multiplexer of claim 5, wherein, the
filters in said wavelength division multiplexer are thin film
filters, and the uplink band in said upgrade band is 1260
nm.about.1280 nm, and the downlink band in said uplink band is 1550
nm.about.1580 nm; the uplink band in said basic band is 1290
nm.about.1330 nm, that is, a O band, and the downlink band in said
basic band is 1480 nm.about.1500 nm, that is, a S band.
17. A wavelength division multiplexer of claim 6, wherein, the
filters in said wavelength division multiplexer are thin film
filters, and the uplink band in said upgrade band is 1260
nm.about.1280 nm, and the downlink band in said uplink band is 1550
nm.about.1580 nm; the uplink band in said basic band is 1290
nm.about.1330 nm, that is, a O band, and the downlink band in said
basic band is 1480 nm.about.1500 nm, that is, a S band.
18. A wavelength division multiplexer of claim 7, wherein, the
filters in said wavelength division multiplexer are thin film
filters, and the uplink band in said upgrade band is 1260
nm.about.1280 nm, and the downlink band in said uplink band is 1550
nm.about.1580 nm; the uplink band in said basic band is 1290
nm.about.1330 nm, that is, a O band and the downlink band in said
basic band is 1480 nm.about.1500 nm, that is, a S band.
19. A wavelength division multiplexer of claim 8, wherein, the
filters in said wavelength division multiplexer are thin film
filters, and the uplink band in said upgrade band is 1260
nm.about.1280 nm, and the downlink band in said uplink band is 1550
nm.about.1580 nm; the uplink band in said basic band is 1290
nm.about.1330 nm that is, a O band, and the downlink band in said
basic band is 1480 nm.about.1500 nm, that is, a S band.
20. A wavelength division multiplexer of claim 9, wherein, the
filters in said wavelength division multiplexer are thin film
filters, and the uplink band in said upgrade band is 1260
nm.about.1280 nm, and the downlink band in said uplink band is 1550
nm.about.1580 nm; the uplink band in said basic band is 1290
nm.about.1330 nm, that is, a O band, and the downlink band in said
basic band is 1480 nm.about.1500 nm, that is, a S band.
21. A wavelength division multiplexer of claim 10, wherein, the
filters in said wavelength division multiplexer are thin film
filters, and the uplink band in said upgrade band is 1260
nm.about.1280 nm, and the downlink band in said uplink band is 1550
nm.about.1580 nm; the uplink band in said basic band is 1290
nm.about.1330 nm, that is, a O band, and the downlink band in said
basic band is 1480 nm.about.1500 nm, that is, a S band.
Description
TECHNICAL FIELD
[0001] The present invention relates to the next generation-passive
optical network (NG-PON) combining technologies of Time Division
Multiplexing (TDM) and Wavelength Division Multiplexing (WDM) in
the field of optical access network communication, and more
especially, to a wavelength division multiplexer for upgrading the
existing time division multiplexing-passive optical network
(TDM-PON) including the ATM-PON, Broadband-PON, Ethernet-PON and
Gigabit-PON to the NG-PON or making the existing TDM-PON compatible
with the NG-PON.
BACKGROUND OF THE RELATED ART
[0002] Optical access network is generally evolving from the
broadband passive optical network (B-PON), Gigabit Passive Optical
Network (G-PON) and Ethernet Passive Optical Network (E-PON) based
on the TDM technology to the NG-PON with multiple wavelengths and
high speed based on the combination of the TDM and WDM
technologies. Two-way high-speed transmission with multi-wavelength
single optical fiber between the optical line terminal (OLT) and
the optical network unit (ONU) significantly improves the optical
fiber utility.
[0003] For the G-PON, the uplink and downlink transmission optical
spectrum ranges of the current TDM-PON are specified respectively
as that, the range of the downlink S band .lamda..sub.s is 1480
nm.about.1500 mm, and in order to coexist with the NG-PON, the
range of the uplink O band .lamda..sub.o is 1290 nm.about.1330 nm.
ITU-T optical access network G.984.5 mentions that the OLT in the
existing TDM-PON is called the legacy OLT, and its working band is
the basic band .lamda..sub.o+s. The OLT in the NG-PON is called the
Upgrade OLT. The full service access networks (FSAN) organization
specifies the wavelength of the NG-PON, the range of whose uplink
wavelength is 1260 nm.about.1280 nm, and the range of whose
downlink wavelength is 1575 nm.about.1580 nm, and it also specifies
that the wavelength range of the CATV downlink signal is 1550
nm.about.1560 nm.
[0004] In order to implement the architecture for the TDM-PON to
smoothly upgrade into the NG-PON system or to be compatible with
the NG-PON system, wavelength division multiplexing 1 (WDM1,
G.984.5 specifies that the name of the wavelength division
multiplexer for making the NG-PON compatible with the existing time
division multiplexing PON is WDM1) should be inserted between the
legacy OLT, the upgrade OLT and the splitter to make the existing
TDM-PON and the NG-PON transmit optical signals in different bands
with a single optical fiber in the same optical distribution
network (ODN), as shown in FIG. 1. WDM1 can make the ODN in the
existing TDM-PON transmit the NG-PON optical signal to achieve the
smooth upgrading from the TDM-PON to the NG-PON.
[0005] Since WDM1 requires high optical signal working band
isolation, low optical network insert loss, high practicality, and
high performance to price ratio, there is no scheme to implement
the WDM1 device module in the prior art.
SUMMARY OF THE PRESENT INVENTION
[0006] The technical problem to be solved by the present invention
is to provide a wavelength division multiplexer compatible with two
PONs so as to achieve the wavelength division multiplexing and
de-multiplexing of the optical signals in the basic and upgrade
bands.
[0007] In order to solve the above problem, the present invention
provides a wavelength division multiplexer compatible with two PONs
to achieve the compatibility of the NG-PON with the existing
TDM-PON, wherein, said existing TDM-PON uses the basic band while
the NG-PON uses the upgrade band, and both said basic band and
upgrade band comprise upstream and downstream bands, said
wavelength division multiplexer comprises the upgrade OLT port, the
legacy OLT port and the common port, wherein:
[0008] The wavelength division multiplexer also comprises one or
more filters, which are used to, in downlink direction, to
multiplex an optical signal in a basic band input from the legacy
optical line terminal port and an optical signal in an upgrade band
input from the upgrade optical line terminal port, and to output
the multiplexed optical signal via the common port; in an uplink
direction, to de-multiplex a wavelength division multiplexed
optical signal input from the common port into the optical signal
in the basic band and that in the upgrade band respectively, and to
output the optical signal in the basic band via the legacy optical
line terminal port and the optical signal in the upgrade band via
the upgrade optical line terminal port.
[0009] Furthermore, the above wavelength division multiplexer may
further have the following features: the wavelength division
multiplexer comprises a plurality of filters, and the filters meet
the following conditions:
[0010] there is at least one filter whose transmission band
comprises the uplink band in the basic band and reflection band
comprises the uplink band in the upgrade band in an uplink optical
channel from a filter de-multiplexing the optical signals in the
two uplink bands to the legacy optical line terminal port;
[0011] there is at least one filter whose transmission band
comprises the uplink band in the upgrade band and the reflection
band comprises the uplink band in the basic band in an uplink
optical channel from the filter de-multiplexing optical signals in
the two uplink bands to the upgrade optical line terminal port;
[0012] there is at least one filter whose transmission band
comprises the downlink band in the basic band and reflection band
comprises a downlink band in the upgrade band in a downlink optical
channel from the legacy optical line terminal port to a filter
multiplexing optical signals in the two downlink bands; and
[0013] there is at least one filter whose transmission band
comprises the downlink band in the upgrade band and reflection band
comprises the downlink band in the basic band in a downlink optical
channel from the upgrade optical line terminal port to the filter
multiplexing optical signals in the two downlink bands.
[0014] Furthermore, the above wavelength division multiplexer may
further have the following features: said wavelength division
multiplexer comprises a first filter, a second filter, a third
filter and a fourth filter, and there are optical channels between
the upgrade optical line terminal port and the common port of the
first filter, between the reflection port of the first filter and
the transmission port or the common port of the fourth filter,
between the common port or the transmission port of the fourth
filter and the reflection port of the third filter, between the
transmission port of the first filter and the reflection port of
the second filter, between the legacy optical line terminal port
and the transmission port of the second filter, between the common
port of the second filter and the transmission port of the third
filter, and between the common port of said wavelength division
multiplexer and the common port of the third filter.
[0015] Furthermore, the above wavelength division multiplexer may
further have the following features: said first filter is a
band-pass or sideband filter, and the transmission band of said
first filter comprises the downlink band in the upgrade band and
the reflection band of said first filter comprises the basic band
and the uplink band in the upgrade band; said second filter is a
sideband filter, and the transmission band of the second filter
comprises the basic band and the uplink band in the upgrade band,
and the reflection band of said second filter comprises the
downlink band in the upgrade band; said third filter is a sideband
filter, and the transmission band of said third filter comprises
the downlink band in the upgrade band and the basic band, and the
reflection band of said third filter comprises the uplink band in
the upgrade band; said fourth filter is a band-pass or sideband
filter, and the transmission band of the fourth filter comprises
the uplink band in the upgrade band, and the reflection band of the
fourth filter comprises the downlink band in the upgrade band and
the basic band; alternatively
[0016] said first filter is a band-pass or sideband filter, and the
transmission band of said first filter comprises the uplink band in
the upgrade band, the reflection band of said first filter
comprises the downlink band in the upgrade band and the basic band;
said second filter is a sideband filter, and the transmission band
of said second filter comprises the downlink band in the upgrade
band and the basic band, the reflection band of said second filter
comprises the uplink band in the upgrade band; said third filter is
a sideband filter, and the transmission band of the third filter
comprises the uplink band in the upgrade band and the basic band,
the reflection band of the third filter comprises the downlink band
in the upgrade band; said fourth filter is a band-pass or sideband
filter, and the transmission band of the fourth filter comprises
the downlink band in the upgrade band, the reflection band of the
fourth filter comprises the basic band and the uplink band in the
upgrade band.
[0017] Furthermore, the above wavelength division multiplexer may
further have the following features: said wavelength division
multiplexer comprises a first filter, a second filter, a third
filter and a fourth filter, and there are optical channels between
the upgrade optical line terminal port and the common port of the
first filter, between the reflection port of the first filter and
the transmission port of the third filter, between the transmission
port of the first filter and the reflection port of the second
filter, between the transmission port of the second filter and the
transmission port or the common port of the fourth filter, between
the common port of the second filter and the reflection port of the
third filter, between the common port of the third filter and the
common port of said wavelength division multiplexer, and between
the common port or the transmission port of said fourth filter and
the legacy optical line terminal port.
[0018] Furthermore, the above wavelength division multiplexer may
further have the following features: said first filter is a
band-pass or sideband filter, and the transmission band of the
first filter comprises the downlink band in the upgrade band, the
reflection band of the first filter comprises the uplink band in
the upgrade band and the basic band; said second filter is a
sideband filter, and the transmission band of said second filter
comprises the uplink band of the upgrade band and the basic band,
the reflection band of said second filter comprises the downlink
band in the upgrade band; said third filter is a band-pass or
sideband filter, and the transmission band of the third filter
comprises the uplink band in the upgrade band, the reflection band
of the third filter comprises the downlink band in the upgrade band
and the basic band; said fourth filter is a sideband filter, and
the transmission band of the fourth filter comprises the downlink
band in the upgrade band and the basic band, the reflection band of
the fourth filter comprises the uplink band in the upgrade band;
alternatively
[0019] said first filter is a band-pass or sideband filter, and the
transmission band of the first filter comprises the uplink band in
the upgrade band, the reflection band of the first filter comprises
the downlink band in the upgrade band and the basic band; said
second filter is a sideband filter, and the transmission band of
the second filter comprises the downlink band in the upgrade band
and the basic band, the reflection band of the second filter
comprises the uplink band in the upgrade band; said third filter is
a band-pass or sideband filter, and the transmission band of the
third filter comprises the downlink band in the upgrade band, the
reflection band of the third filter comprises the uplink band in
the upgrade band and the basic band; said fourth filter is a
sideband filter, and the transmission band of the fourth filter
comprises the uplink band in the upgrade band and the basic band,
the reflection band of the fourth filter comprises the downlink
band in the upgrade band.
[0020] Furthermore, the above wavelength division multiplexer may
further have the following features: said wavelength division
multiplexer comprises a first filter, a second filter, a third
filter and a fourth filter, and there are optical channels between
the upgrade optical line terminal port and the common port of the
first filter, between the reflection port of the first filter and
the transmission port or the common port of the second filter,
between the transmission port of the first filter and the
reflection port of the fourth filter, between the common port or
the transmission port of the second filter and the reflection port
of the third filter, between the common port of the third filter
and the transmission port of the fourth filter, between the
transmission port of the third filter and the legacy optical line
terminal port, and between the common port of the fourth filter and
the common port of said wavelength division multiplexer.
[0021] Furthermore, the above wavelength division multiplexer may
further have the following features: said first filter is a
band-pass or sideband filter, and the transmission band of the
first filter comprises the uplink band in the upgrade band, the
reflection band of the first filter comprises the downlink band in
the upgrade band and the basic band; said second filter is a
band-pass or sideband filter, and the transmission band of the
second filter comprises the downlink band in the upgrade band, the
reflection band of the second filter comprises the uplink band in
the upgrade band and the basic band; said third filter is a
band-pass or sideband filter, and the transmission band of the
third filter comprises the uplink band in the upgrade band and the
basic band, the reflection band of the third filter comprises the
downlink band in the upgrade band; said fourth filter is a sideband
filter, and the transmission band of the fourth filter comprises
the downlink band in the upgrade band and the basic band, the
reflection band of the fourth filter comprises the uplink band in
the upgrade band; alternatively
[0022] said first filter is a band-pass or sideband filter, and the
transmission band of the first filter comprises the downlink band
in the upgrade band, the reflection band of the first filter
comprises the uplink band in the upgrade band and the basic band;
said second filter is a band-pass or sideband filter, and the
transmission band of the second filter comprises the uplink band in
the upgrade band, the reflection band of the second filter
comprises the downlink band in the upgrade band and the basic band;
said third filter is an sideband filter, and the transmission band
of the third filter comprises the downlink band in the upgrade band
and the basic band, the reflection band of the third filter
comprises the uplink band in the upgrade band; said fourth filter
is a sideband filter, and the transmission band of the fourth
filter comprises the uplink band in the upgrade band and the basic
band, the reflection band of the fourth filter comprises the
downlink band in the upgrade band.
[0023] Furthermore, the above wavelength division multiplexer may
further have the following features: said wavelength division
multiplexer comprises a band-pass filter, and there are optical
channels between a transmission port of the band-pass filter and
the legacy optical line terminal port, between a common port of the
band-pass filter and the common port of said wavelength division
multiplexer, and between a reflection port of the band-pass filter
and the upgrade optical line terminal port; and a transmission band
of the band-pass filter comprises the basic band, and a reflection
band of the band-pass filter comprises the upgrade band;
alternatively
[0024] there are optical channels between the transmission port of
the band-pass filter and the upgrade optical line terminal port,
between the common port of the filter and the common port of said
wavelength division multiplexer, and between the reflection port of
the filter and the legacy optical line terminal port, and the
transmission band of the band-pass filter comprises the upgrade
band and the reflection band of the band-pass filter comprises the
basic band.
[0025] Furthermore, the above wavelength division multiplexer may
further have the following features: composition of a plurality of
filters of the wavelength division multiplexer and spectral
properties of the filters are in one of the following modes:
[0026] mode 1: said wavelength division multiplexer comprises a
first filter, a second filter and a third filter, the transmission
band of the first filter comprises the downlink band in the upgrade
band, and the reflection band of the first filter comprises the
uplink band in the upgrade band and the basic band; the
transmission band of the second filter comprises the uplink band in
the upgrade band, and the reflection band of the second filter
comprises the downlink band in the upgrade band and the basic band;
the transmission band of the third filter comprises the basic band,
and the reflection band of the third filter comprises the upgrade
band; in connection, there are optical channels between the upgrade
optical line terminal port and a common port of the first filter,
between a reflection port of the first filter and a transmission
port of the second filter, between a transmission port of the first
filter and a reflection port of the second filter, between a common
port of the second filter and a reflection port of the third
filter, between a transmission port of the third filter and the
legacy optical line terminal port, and between a common port of the
third filter and a common port of said wavelength division
multiplexer;
[0027] mode 2: positions of the first filter and the second filter
in mode 1 are exchanged, and the spectral property of each filter
is the same as that in mode 1;
[0028] mode 3: said wavelength division multiplexer comprises a
first filter and a second filter, a transmission band of the first
filter comprises the basic band and a reflection band of the first
filter comprises the upgrade band; a transmission band of the
second filter comprises the upgrade band and the reflection band of
the second filter comprises the basic band; in connection, there
are optical channels between the legacy optical line terminal port
and the transmission port of the first filter, between a common
port of the wavelength division multiplexer and a common port of
the first filter, between the upgrade optical line terminal port
and a transmission port or a common port of the second filter, and
between the common port or the transmission port of the second
filter and a reflection port of the first filter;
[0029] mode 4, said wavelength division multiplexer comprises a
first filter and a second filter, a transmission band of the first
filter comprises the upgrade band and a reflection band of the
first filter comprises the basic band; a transmission band of the
second filter comprises the basic band and a reflection band of the
second filter comprises the upgrade band; in connection, there are
optical channels between a transmission port of the first filter
and the upgrade optical line terminal port, between a reflection
port of the first filter and a transmission port or a common port
of the second filter, between a common port of the first filter and
a common port of said wavelength division multiplexer, and between
the common port or the transmission port of the second filter and
the legacy optical line terminal port;
[0030] mode 5: said wavelength division multiplexer comprises a
first filter, a second filter and an third filter, a transmission
band of the first filter comprises the upgrade band and a
reflection band of the first filter comprises the basic band; a
transmission band of the second filter comprises the uplink band in
the upgrade band and the basic band and a reflection band of the
second filter comprises the downlink band in the upgrade band; a
transmission band of the third filter comprises the downlink band
in the upgrade band and the basic band and a reflection band of the
third filter comprises the uplink band in the upgrade band; in
connection, there are optical channels between a transmission port
of the first filter and the upgrade optical line terminal port,
between a common port of the first filter and a common port of said
wavelength division multiplexer, between a reflection port of the
first filter and a common port or a transmission port of the second
filter, between the transmission port or the common port of the
second filter and the common port or the transmission port of the
first filter, and between the transmission port or the common port
of the first filter and the legacy optical line terminal port;
[0031] mode 6: positions of the second filter and the third filter
in mode 5 are exchanged, and the spectral property of each filter
is the same as that in mode 5.
[0032] Furthermore, the above wavelength division multiplexer may
further have the following features: the filters in said wavelength
division multiplexer are thin film filters.
[0033] Furthermore, the above wavelength division multiplexer may
further have the following features: the uplink band in said
upgrade band is 1260 nm.about.1280 nm, and the downlink band in
said uplink band is 1550 nm.about.1580 nm; the uplink band in said
basic band is 1290 nm.about.1330 nm, that is, the O band, and the
downlink band in said basic band is 1480 nm.about.1500 nm, that is,
the S band.
[0034] WDM1 provided by the present invention implements the
wavelength division multiplexing and de-multiplexing of the optical
signals in the basic and upgrade bands. It makes the ODN in the
existing TDM-PON able to transport the NG-PON at the same time, so
as to smoothly upgrade the deployed TDM-PON to the NG-PON and
provide subsequent network compatibility to the deployed TDM-PON
system. In some embodiments, relatively low cost can still meet the
high isolation requirement of the optical signal in working band by
reasonably using the thin film filters and selecting the spectral
properties of the filters, moreover, the requirements for the
isolation and the optical network insert loss can be taken into
account by setting the number of filters and their spectral
properties. A simple but practical technology applied in the
embodiment of the present invention implements WDM1 with low lost
and high, moreover, the system is easy to use and upgrade.
BRIEF DESCRIPTION OF DRAWINGS
[0035] FIG. 1 illustrates the structure of the external interfaces
of WDM1 in accordance with an embodiment of the present
invention;
[0036] FIG. 2 (a) illustrates the structure of WDM1 in accordance
with a first embodiment of the present invention, and it
illustrates the optical transmission paths in uplink and downlink
directions; FIG. 2 (b).about.FIG. 2 (i) respectively illustrate the
spectral property of each filter in the first embodiment and its
alternatives;
[0037] FIG. 3 (a) illustrates of the structure of WDM1 in
accordance with a second embodiment of the present invention; FIG.
3 (b).about.FIG. 3 (d) respectively illustrate the spectral
property of each filter in the second embodiment;
[0038] FIG. 4 (a) illustrates the structure of WDM1 in accordance
with a third embodiment of the present invention; FIG. 4 (b)
illustrates the spectral property of the filter in the third
embodiment;
[0039] FIG. 5 (a) illustrates the structure of WDM1 in accordance
with a fourth embodiment of the present invention; FIG. 5 (b)
illustrates the spectral property of the filter in the fourth
embodiment;
[0040] FIG. 6 (a) illustrates the structure of WDM1 in accordance
with a fifth embodiment of the present invention; FIG. 6
(b).about.FIG. 6 (c) respectively illustrate the spectral property
of each filter in the fifth embodiment;
[0041] FIG. 7 (a) illustrates the structure of WDM1 in accordance
with a sixth embodiment of the present invention; FIG. 7
(b).about.FIG. 7 (c) respectively illustrate the spectral property
of each filter in the sixth embodiment;
[0042] FIG. 8 (a) illustrates the structure of WDM1 in accordance
with a seventh embodiment of the present invention; FIG. 8
(b).about.FIG. 8 (d) respectively illustrate the spectral property
of each filter in the seventh embodiment;
[0043] FIG. 9 (a) illustrates the structure of WDM1 in accordance
with an eighth embodiment of the present invention; FIG. 9
(b).about.FIG. 9 (d) respectively illustrate the spectral property
of each filter in the eighth embodiment;
[0044] FIG. 10 (a) illustrates the structure of WDM1 in accordance
with a ninth embodiment of the present invention; FIG. 10
(b).about.FIG. 10 (d) respectively illustrate the spectral property
of each filter in the ninth embodiment;
[0045] FIG. 11 (a) illustrates the structure of WDM1 in accordance
with a tenth embodiment of the present invention; FIG. 11
(b).about.FIG. 11 (i) respectively illustrate the spectral property
of each filter in the tenth embodiment and its alternatives;
[0046] FIG. 12 (a) illustrates the structure of WDM1 in accordance
with an eleventh embodiment of the present invention; FIG. 11
(b).about.FIG. 11 (e) respectively illustrate the spectral property
of each filter in the eleventh embodiment;
[0047] FIG. 13 is a diagram of the network structure of WDM1
implementing the compatibility of the NG-PON with the G-PON in
accordance with an embodiment of the present invention.
PREFERRED EMBODIMENTS OF THE PRESENT INVENTION
[0048] The embodiments of the present invention will be described
in detail with reference to the accompanying figures.
[0049] When the existing TDM-PON on a single optical fiber evolves
into the NG-PON, three bands, respectively the uplink band (1260
nm.about.1280 nm) of the NG-PON, the downlink band (1550
nm.about.1560 nm) of the CATV signals, and the downlink L band
(1575 nm.about.1580 nm) of the NG-PON, will be introduced.
Therefore, the upgrade band in the context comprises an uplink band
and a downlink band, wherein, the uplink band is 1260 nm.about.1280
nm and the downlink band is 1550 nm.about.1580 nm, including 1550
nm.about.1560 nm and 1575 nm.about.1580 nm. While the basic band
also comprises an uplink band and a downlink band, wherein, the
uplink band is 1290 nm.about.1330 nm, that is, the O band, and the
downlink band is 1480 nm.about.1500 nm, that is, the S band. It
should be noted that, the above wavelength assignment can be
modified, as long as the distribution relationship of the above
four bands is unchanged, WDM1 in the present invention still can be
used.
[0050] In order to smoothly upgrade the TDM-PON on the single
optical fiber to the NG-PON, one of the key problems is to insert a
WDM1 between the OLT and the splitter to implement the wavelength
division multiplexing of the optical signals in the basic and
upgrade bands, meanwhile meeting as much as possible the
requirement of low cost, high reliability, easy-for-use and
easy-for-system upgrade. As the access point of the optical signals
with different wavelengths, the wavelength division multiplexer
needs to meet the following requirements:
[0051] A. implement the functions of wavelength division multiplex
and de-multiplex of the wavelength division multiplexed optical
signal in the NG-PON and the optical signal in the existing TDM-PON
in the existing ODN;
[0052] B. keep high isolation between the optical signal in the
basic band and that in the upgrade band; and
[0053] C. have low insert loss.
[0054] In the fabricating technology of the filter used as the
wavelength division multiplexer, thin film filter is relatively
suitable to be a broadband filter and its fabricating technology is
relatively mature, therefore, it can be used in WDM1. The thin film
filter has the functions of transmission and reflection, and the
corresponding working bands can be called as the transmission band
and the reflection band. For common thin film filters, the
isolation of the transmission port typically works well enough that
it is less possible to interfere with the optical signals in other
bands, the isolation can reach 35 dB. While the isolation of the
reflection port is relatively worse, which is 15 dB, and the
optical signals in the transmission band can interfere with those
in the reflection port, and enforced measurements should be
adopted. The insert loss is proportional with the number of thin
film filters. Therefore, the minimum number of filters is preferred
as long as the isolation meets the requirement. The following
embodiments are implemented with thin film filters, however, the
present invention does not limit the type of the adopted filter,
and any filter which can achieve the same spectral property can be
applied in WDM1 in the present invention.
[0055] In the network system architecture of the NG-PON compatible
with the existing TDM-PON, the central office is configured with
the legacy OLT and the upgrade OLT, and the external interfaces of
WDM1 are as shown FIG. 1, and the interfaces comprise the legacy
OLT port, the upgrade OLT port and the common port:
[0056] In the downlink direction, the optical signals in the basic
band are input to the legacy OLT port, the optical signals in the
upgrade band are input to the upgrade OLT port, the wavelength
division multiplexer multiplexes the input optical signal in the
basic band and that in the upgrade band and outputs the multiplexed
signal to the common port, so that the optical signals in two bands
are transmitted in a single optical fiber and transmitted to each
ONU device via optical devices such as the splitter; in uplink
direction, the wavelength division multiplexed optical signals in
the two bands are input from the common port of WDM1 via the same
optical fiber, and WDM1 de-multiplexes the optical signals and
sends the optical signals in the basic band to the legacy OLT port
and those in the upgrade band to the upgrade OLT port
respectively.
[0057] The whole bandwidth of the basic band is 210 nm (the range
of the downlink S band is 1480 nm.about.1500 nm, and the range of
the uplink O band is 1290 nm.about.1330 nm), the uplink and
downlink bands of the upgrade band are distributed outside the
basic band in both sides (uplink band is 1260 nm.about.1280 nm, and
the downlink band is 1550 nm.about.1580 nm, herein the downlink
band comprises two parts, the CATV downlink band and the NG-PON
downlink band). Therefore, it can be seen that the interval between
the uplink band in the basic band and the uplink band in the
upgrade band is relatively narrow, about 10 nm. Therefore, the
bandwidth of the basic band is relatively wide, and the band
interval between the two bands is relatively narrow.
[0058] The present invention will be illustrated with embodiments
in the following. It should be understood that the preferred
embodiments to be described in the following are only used to
illustrate and explain rather than to limit the present invention.
In the case that there is no conflict, the embodiments and features
in the embodiments in this application can be combined.
[0059] The specific structure of a plurality of embodiments for
implementing WDM1 will be described in further detail with
reference to the accompanying figures:
The First Embodiment
[0060] Due to factors such as the WDM1 fabricating technology, the
requirement of telecommunication network application and the cost,
WDM1 can be assembled with the sideband filters and/or band-pass
filters according to the features of the basic and upgrade
bands.
[0061] FIG. 2(a) illustrates the structure of WDM1 and its working
principle in uplink/downlink direction in accordance with this
first embodiment, and this WDM1 comprises four thin film filters:
the band-pass filter f11, the sideband filter f12, the sideband
filter f13 and the band-pass filter f14. Both the sideband and the
band-pass filter can be three-port devices including a transmission
port, a reflection port and a common port. Some band-pass or
sideband filter such as f14 might be a two-port device including a
transmission port and a common port. In FIG. 2 (a), the reflection
port and the common port are at the same side of the filter, while
the transmission port is at the other side. The reflection port is
in the direction opposite to the arrow in the transmission port
line (toward or depart from the filter).
[0062] Refer to the spectrums illustrated in FIG. 2(b).about.FIG.
2(e). The transmission band of the band-pass filter f11 includes
1550 nm.about.1580 nm, and the reflection band of f11 includes 1260
nm.about.1500 nm; the transmission band of the band-pass filter f12
includes 1260 nm.about.1500 nm, and the reflection band of f12
includes 1500 nm.about.1580 nm; the transmission band of the
sideband filter f13 includes 1290 nm.about.1580 nm, the reflection
band of f13 includes 1260 nm.about.1280 nm; the transmission band
of the band-pass filter f14 includes 1260 nm.about.1280 nm, and the
reflection band of f14 includes 1290 nm.about.1580 nm.
[0063] Refer to FIG. 2(a), there are optical channels between the
upgrade OLT port and the common port of the band-pass filter f11,
between the reflection port of the band-pass filter f11 and the
transmission port of the band-pass filter f14, between the common
port of the band-pass filter f14 and the reflection port of the
sideband filter f13, between the transmission port of the band-pass
filter f11 and the reflection port of the sideband filter f12,
between the legacy OLT port and the transmission port of the
sideband filter f12, between the common port of the sideband filter
f12 and the transmission port of the sideband filter f13, and
between the WDM1 common port and the common port of the sideband
filter f13. The common port and the transmission port of f14 can be
exchanged. For convenience, some optical channels in FIG. 2 (a) are
represented with polygonal lines, while the optical channels in the
practical device are usually represented with straight line,
although there is still the case that the transmission direction of
the optical signals in an optical channel might change by adding
reflection devices. The other embodiments are similar. The arrows
in FIG. 2 (a) are shown taking the downlink direction as an
example; however, the uplink direction can be achieved by reversing
all the arrow directions.
[0064] In the downlink direction, after the downlink signal (whose
wavelength is between 1550 nm and 1580 nm) in the NG-PON inputs
from the upgrade OLT port of WDM1, it enters into the common port
of the band-pass filter f11, and after transmitted through the
band-pass filter f11, the signal enters into the sideband filter
f12, after reflected by the sideband filter f12, the signal enters
into the transmission port of the sideband filter f13, and after
transmitted through f13, the signal is output to the common port of
WDM1 via the common port of the sideband filter f13; meanwhile, the
downlink signal in the G-PON (whose wavelength is between 1480 nm
and 1500 nm) enters into the transmission port of the sideband
filter f12 after transmitted from the legacy OLT port of WDM1, and
then enters into the transmission port of the sideband filter f13
after output from the common port of the sideband filter f12, and
after transmitted through the transmission port of f13, the signal
is output from the common port of the sideband filter f13 to the
common port of WDM1. Therefore, the signal output from the common
port of WDM1 is the signal generated by wavelength division
multiplexing the NG-PON downlink signal and the G-PON downlink
signal.
[0065] In the uplink direction, the wavelength division multiplexed
signal input from the common port of WDM1 comprises the uplink
signal in the GN-PON (between 1260 nm and 1280 nm) and the uplink
signal in the G-PON (between 1290 nm and 1330 nm), wherein, the
uplink signal in the NG-PON enters into the common port of the
sideband filter f13 after transmitted from the common port of WDM1,
and then enters into the common port of the band-pass filter f14
after reflected by the sideband filter f13, then the signal is
output to the reflection port of the band-pass filter f11 via the
transmission port of f14 after transmitted through f14, and then
output to the upgrade OLT port of WDM1 via the common port of f11
after reflected by f11; meanwhile, the uplink signal in the G-PON
enters into the common port of the sideband filter f13 after input
from the common port of WDM1, and then enters into the common port
of the sideband filter f12 after output from the transmission port
of f13, and then output to the legacy OLT port of WDM1 via the
transmission port of f12 after transmitted through the sideband
filter f12. The de-multiplexing is completed.
[0066] Not only implementing the wavelength division multiplexing
and de-multiplexing, the WDM1 in the present embodiment can also
meet the requirement of high isolation between the upgrade band and
the basic band. The interference between the uplink band in the
upgrade band and the uplink band in the basic band, and between the
downlink band in the basic band and the downlink band in the
upgrade band should be taken into account.
[0067] It has been mentioned that there is high isolation at the
transmission port of the filter, if there is at least one filter
whose transmission band comprises the uplink band in the basic band
and reflection band comprises the uplink band in the upgrade band
in the uplink optical channel from the filter de-multiplexing the
optical signals in the two uplink bands to the legacy OLT port of
WDM1 (including the de-multiplexing filter), and there is at least
one filter whose transmission band comprises the uplink band in the
upgrade band and reflection band comprises the uplink band in the
basic band in the uplink optical channel from the filter for
de-multiplexing the optical signals in the two uplink bands to the
upgrade OLT port of WDM1 (including the filter for
de-multiplexing), regular filters can meet the requirement of
isolation between the two uplink bands. If there is at least one
filter whose transmission band comprises the downlink band in the
basic band and reflection band comprises the downlink band in the
upgrade band in the downlink optical channel from the legacy OLT
port of WDM1 to the filter for multiplexing the optical signals in
the two downlink bands (including the multiplexing filter), and
there is at least one filter whose transmission band comprises the
downlink band in the upgrade band and reflection band comprises the
downlink band in the basic band in the downlink optical channel
from the upgrade OLT port of WDM1 to the filters for multiplexing
the optical signals in the two downlink bands (including the
multiplexing filter), the requirement of isolation between the two
downlink bands can be met. The above four conditions are
collectively called as the first isolation condition in the
following.
[0068] The present embodiment can meet this requirement, and the
filter for de-multiplexing the optical signals in the two uplink
bands is f13, and the filters in the uplink optical channel from
f13 to the legacy OLT port comprise f13 and f12, the uplink band in
the basic band falls within the transmission band of f13 and the
uplink band in the upgrade band falls within the reflection band of
f13. The filters in the uplink optical channel from f13 to the
upgrade OLT port comprise f13, f14 and f11, wherein, the uplink
band in the upgrade band falls within the transmission band of f14
and the uplink band in the basic band falls within the reflection
band of f14. Moreover, the filter for multiplexing the optical
signals in the two downlink bands is f12 (multiplexing two signals
means that two signals are separate from each other when being
input into the filter and will be combined into one when being
output), the filters in the downlink optical channel from the
legacy OLT port to f12 is f12, and the transmission band of f12
comprises the downlink band in the basic band and the reflection
band of f12 comprises the downlink band in the upgrade band, the
filters in the downlink optical channel from the upgrade OLT port
to f12 comprise f11 and f12, the transmission band of f11 comprises
the downlink band in the upgrade band and the reflection band in
f11 comprises the downlink band in the basic band. Therefore, the
present embodiment can guarantee the isolation between the two
uplink bands as well as that between two downlink bands, moreover,
all filters can be implemented with regular filters, so as to
decrease the cost of WDM1, and some variations can be obtained by
modifying the types of the above filters and their spectral
properties:
[0069] Variation 1, whose structural diagram is still as shown in
FIG. 2 (a), and its spectrograms are as shown in FIG. 2
(f).about.FIG. 2(i), and the band-pass filter f11 is modified to an
sideband filter, 1550 nm.about.1580 nm is in its transmission band
and 1260 nm.about.1500 nm is in its reflection band; the band-pass
filter f14 is modified to a sideband filter, 1260 nm.about.1280 nm
is in its transmission band, and 1290 nm.about.1580 nm is in its
reflection band. While the types and spectral properties of f12 and
f13 keep unchanged. Since the transmission/reflection relationship
of the uplink and downlink bands in the basic band and the uplink
and downlink bands in the upgrade band (also called the four
related bands of WDM1) keep unchanged in the spectral properties of
the filters in this modification, their performance is basically
the same. It is also feasible that only one of f11 and f14 rather
than both of them is changed in this variation.
[0070] Variation two, the structure is still as shown in FIG. 2
(a), f11.about.f14 are all sideband filters, and their spectral
properties are as follows: the transmission band of the sideband
filter f11 comprises 1260 nm.about.1280 nm, and the reflection band
of f11 comprises 1290 nm.about.1580 nm; the transmission band of
the sideband filter f12 comprises 1290 nm.about.1580 nm, and the
reflection band of f12 comprises 1260 nm.about.1280 nm; the
transmission band of the sideband filter f13 comprises 1260
nm.about.1500 nm, and the reflection band of f13 comprises 1550
nm.about.1580 nm; the transmission band of the sideband filter f14
comprises 1550 nm.about.1580 nm, and the reflection band of f14
comprises 1260 nm.about.1500 nm.
[0071] Variation three: on the basis of variation two, the sideband
filter f11 and/or the sideband filter f14 are modified to the
band-pass filters, and the transmission or reflection relationship
of the four related bands in the spectral properties of band-pass
filters f11 and f14 are the same as those of f11 and f14 in
variation two.
[0072] With the similar analysis as given above, the function of
WDM1 can be achieved and the requirement of high isolation can be
met. Similarly, the parameters achieved by said WDM1 device module
are shown in table 1.
TABLE-US-00001 TABLE 1 the parameters of said WDM1 device module
shown in FIG. 2 (a) Specification Value TDM-PON loss range
(connector is not <1.0 dB considered) 1290-1330 nm 1480-1500 nm
NG-PON loss range (connector is not <1.3 dB considered)
1260-1280 nm 1550-1580 nm Isolation - COM - OLT >35 dB 1260-1280
nm 1550-1580 nm Isolation - COM - UPGRADE >35 dB 1260-1280 nm
1550-1580 nm Maximum optical power +23 dBm Return loss >50 dB
Directivity >50 dB
The Second Embodiment
[0073] WDM1 in this embodiment comprises three thin film filters:
the sideband filter f21, the sideband filter f22 and the band-pass
filter f23 respectively. FIG. 3 (b) to FIG. 3 (d) show the spectral
property of each filter respectively. Wherein, 1550 nm.about.1580
nm is in the transmission band of the sideband filter f21, 1260
nm.about.1500 nm is in the reflection band of the sideband filter
f21; 1260 nm.about.1280 nm is in the transmission band of the
sideband filter f22; 1290 nm.about.1580 nm is in the reflection
band of f22; 1290 nm.about.1500 nm is in the transmission band of
the band-pass filter f23, and 1260 nm.about.1280 nm and 1550
nm.about.1580 nm are in the reflection band of f23.
[0074] There are optical channels between the upgrade OLT port of
WDM1 and the common port of the sideband filter f21, between the
reflection port of the sideband filter f21 and the transmission
port of the sideband filter f22, between the transmission port of
the sideband filter f21 and the reflection port of the sideband
filter f22, between the common port of the sideband filter f22 and
the reflection port of the band-pass filter f23, between the
transmission port of the band-pass filter f23 and the legacy OLT
port of WDM1, and between the common port of the band-pass filter
f23 and the common port of WDM1.
[0075] In the downlink direction, after the downlink signal (whose
wavelength is 1550 nm.about.1580 nm) in the NG-PON is input from
the upgrade OLT port of WDM1, it enters into the common port of the
sideband filter f21, and then enters into the reflection port of
the sideband filter f22 after transmitted through the sideband
filter f21, and then the signal is output from the common port of
band-pass filter f22 to the reflection port of the band-pass filter
f23 after reflected by the sideband filter f22, and then output
from the common port of the band-pass filter f23 to the common port
of WDM1 after reflected by f23; meanwhile, the downlink signal
(whose wavelength is in 1480 nm.about.1500 nm) in the G-PON enters
into the transmission port of the band-pass filter f23 after
transmitted from the legacy OLT port of WDM1, and after transmitted
by the band-pass filter f23, the signal is output from the common
port of f23 to the common port of WDM1 for output, therefore, the
signal output from the common port of WDM1 is the signal generated
by wavelength division multiplexing the downlink signal in the
NG-PON and that in the G-PON.
[0076] In the uplink direction, the wavelength division multiplexed
signals input from the common port of WDM1 comprise the uplink
signal in the NG-PON and the uplink signal in the G-PON, wherein,
the uplink signal in the NG-PON enters into the common port of the
band-pass filter f23 after transmitted from the common port of
WDM1, and after reflected by the band-pass filter f23, the signal
is output by the reflection port of f23 and enters into the common
port of the sideband filter f22, and after transmitted through f22,
the signal is output to the reflection port of the sideband filter
f21 from the transmission port of the sideband filter f22, and
after reflected by the sideband filter f21, the signal is output to
the upgrade OLT port of WDM1 from the common port of f21;
meanwhile, the uplink signal in the G-PON enters into the common
port of the band-pass filter f23 after transmitted from the common
port of WDM1, and after transmitted by the band-pass filter f23,
the signal is output to the legacy OLT port of WDM1 via the
transmission port of the band-pass filter f23.
[0077] It can be seen that this embodiment also meets the above
first isolation condition. Since the difficulty in fabricating
technology of the thin film filter is proportional to the band-pass
width and isolation of the filter, while reversely proportional to
the protection bandwidth interval. The sideband filter f21 and the
sideband filter f22 enhance the isolation in the reflection
direction, and indirectly decrease the requirement of isolation in
the reflection direction of the band-pass filter f23, and therefore
decrease the difficulty in fabricating the thin film filter, which
reduces the number of coating layers in the thin film filter and
the fabricating difficulty, so as each filter in the first
embodiment. Moreover, since the band-pass width of the band-pass
filter f23 in this embodiment is relatively large, the band-pass
filter f23 is more difficult to be implemented compared to the
filter in the first embodiment, and the cost of WDM1 in the first
embodiment is relatively inexpensive.
[0078] The parameters achieved by the WDM1 device module in the
present embodiment are shown in Table 2.
TABLE-US-00002 TABLE 2 the parameters of the WDM1 device module
shown in FIG. 2 (b) Specification Value TDM-PON loss range
(connector is not <0.5 dB considered) 1290-1330 nm 1480-1500 nm
NG-PON loss range (connector is not <1.1 dB considered)
1260-1280 nm 1550-1580 nm Isolation - COM - OLT >35 dB 1260-1280
nm 1550-1580 nm Isolation - COM - UPGRADE >35 dB 1260-1320 nm
1480-1500 nm Maximum optical power +23 dBm Return loss >50 dB
Directivity >50 dB
The Third Embodiment
[0079] When applying a more advanced coating technology, the
band-pass filter f31 can be directly used to implement the above
wavelength division multiplexing/de-multiplexing function, that is,
use the band-pass thin film filter to make the broad band-pass WDM1
with high isolation to implement the wavelength division
multiplexing/de-multiplexing function of the basic and upgrade
bands and the requirements of high isolation, the uplink and
downlink working principles of WDM1 are as shown in FIG. 4 (a), and
there are optical channels between the transmission port of f31 and
the legacy OLT port of WDM1, between the common port of f31 and the
common port of WDM1, and between the reflection port of f31 and the
upgrade OLT port of WDM1.
[0080] FIG. 4 (b) is an illustration of the spectral property of
f31, wherein, 1290 nm.about.1500 nm is in the transmission band of
f31, 1260 nm.about.1280 nm and 1550 nm.about.1580 nm are in the
reflection band of f31. Via the band-pass filter f31, the
multiplexing and de-multiplexing of the optical signals in the
basic and upgrade bands can be directly implemented.
[0081] This embodiment applies a single band-pass filter f31 to
implement the above wavelength division
multiplexing/de-multiplexing function; alternatively, a plurality
of f31s can be assembled together to implement the above wavelength
division multiplexing/de-multiplexing function.
The Fourth Embodiment
[0082] WDM1 in this embodiment also only applies one band-pass
filter f41, as shown in FIG. 5 (a), there are optical channels
between the transmission port of f41 and the upgrade OLT port of
WDM1, between the common port of f41 and the common port of WDM1,
and between the reflection port of f41 and the legacy OLT port of
WDM1.
[0083] FIG. 5 (b) is an illustration of the spectral property of
f41, wherein, 1290 nm.about.1500 nm is in the reflection band of
f41, 1260 nm.about.1280 nm and 1550 nm.about.1580 nm are in the
transmission band of f41. With the band-pass filter f41, the
multiplexing and de-multiplexing of the optical signals in the
basic and upgrade bands can be directly implemented.
The Fifth Embodiment
[0084] As shown in FIG. 6 (a), the WDM1 in this embodiment
comprises the band-pass filter f51 and the band-pass filter f52.
1290 nm.about.1500 nm is in the transmission band of f51, 1260
nm.about.1280 nm and 1550 nm.about.1580 nm are in the reflection
band of f51. 1290 nm.about.1500 nm is in the reflection band of
f52, 1260 nm.about.1280 nm and 1550 nm.about.1580 nm are in the
transmission band of f52.
[0085] In connection, there are optical channels between the legacy
OLT port of WDM1 and the transmission port of f51, between the
common port of WDM1 and the common port of f51, between the upgrade
OLT port of WDM1 and the transmission port of f52, and between the
common port of f52 and the reflection port of f51. The common port
and transmission port of f52 can be exchanged.
[0086] Based on the optical signal transmission path indicated in
FIG. 6(a) (which will not be described in detail here since it is
clearly shown in FIG. 6(a)), the multiplexing and de-multiplexing
of optical signals in the upgrade and basic bands can be achieved,
and the above first isolation condition is meet as well and the
insertion loss is relatively low.
The Sixth Embodiment
[0087] As shown in FIG. 7 (a), WDM1 in this embodiment comprises
the band-pass filters f61 and f62, wherein, the spectral property
of f61 is the same as that of f52 in the fifth embodiment, and the
spectral property of f62 is the same as that of f51 in the fifth
embodiment.
[0088] The connection relationships among the filters as well as
that between the filters and the port of WDM1 change
correspondingly, wherein, there are optical channels between the
transmission port of the band-pass filter f61 and the upgrade OLT
port of WDM1, between the reflection port of f61 and the
transmission port of f62, between the common port of f61 and the
common port of WDM1, and between the common port of f62 and the
legacy OLT port of WDM1. The common port and the transmission port
of f62 can be exchanged.
[0089] Similarly, WDM1 in the present embodiment can achieve the
multiplexing and de-multiplexing of the optical signals in the
upgrade band and basic band, and it also meets the above first
isolation condition and has relatively low insertion loss.
The Seventh Embodiment
[0090] The structure of WDM1 in this embodiment is shown as FIG.
8(a), and the WDM1 comprises the sideband filter f71, the sideband
filter f72 and the band-pass filter f73, the spectral properties of
these three filters are shown respectively from FIG. 8 (b) to FIG.
8 (d). It can be seen that the structure of this embodiment is
basically the same as that of the second embodiment, only
exchanging the positions of sideband filters f51 and f51 in the
second embodiment, while keeping their performances the same.
Therefore, the detailed description of this embodiment will be
omitted here.
The Eighth Embodiment
[0091] As shown in FIG. 9 (a), WDM1 in this embodiment comprises
the band-pass filter f81, the sideband filter f82 and the sideband
filter f83. The transmission band of f82 comprises 1260
nm.about.1500 nm, the reflection band of f82 comprises 1550
nm.about.1580 nm; the transmission band of f83 comprises 1290
nm.about.1580 nm, and the reflection band of f83 comprises 1260
nm.about.1280 nm.
[0092] The spectral property of f81 in this embodiment is the same
as that of f61 in the sixth embodiment. The roles of the two
serially connected sideband filters f82 and f83 are the same as
that of f62, and the overlapped spectral property is the same as
that of f62, although the sideband filters f82 and f83 are more
easily implemented. Therefore, WDM1 in this embodiment can
implement the multiplexing and de-multiplexing of the optical
signals in the upgrade band and the basic band, and it also meets
the above first isolation condition.
The Ninth Embodiment
[0093] The difference between this embodiment and the eighth
embodiment is that the positions of the sideband filters f82 and
f83 in the eighth embodiment are exchanged, and this embodiment
will not be described in detail here.
The Tenth Embodiment
[0094] As shown in FIG. 11 (a), WDM1 in this embodiment comprises
the sideband filters f101, f102, f103 and f104. As shown in FIG. 11
(b).about.(e), the transmission band of the sideband filter f101
includes 1550 nm.about.1580 nm, the reflection band of the sideband
filter f101 includes 1260 nm.about.1500 nm; the transmission band
of the sideband filter f102 includes 1260 nm.about.1500 nm, and the
reflection band of the sideband filter f102 includes 1550
nm.about.1580 nm; the transmission band of the sideband filter f103
includes 1260 nm.about.1280 nm, and the reflection band of the
sideband filter f103 includes 1290 nm.about.1580 nm; the
transmission band of the sideband filter f104 includes 1290
nm.about.1580 nm, and the reflection band of the sideband filter
f104 includes 1260 nm.about.1280 nm.
[0095] There are optical channels between the upgrade OLT port of
WDM1 and the common port of f101, between the reflection port of
f101 and the transmission port of f103, between the transmission
port of f101 and the reflection port of f102, between the
transmission port of f102 and the transmission port of f104,
between the common port of f102 and the reflection port of f103,
between the common port of f103 and the common port of WDM1, and
between the common port of f104 and the legacy OLT port of WDM1.
The common port and the transmission port of f104 can be
exchanged.
[0096] From FIG. 11 (a).about.(e), it can be seen that WDM1 in this
embodiment can implement the wavelength division multiplexing and
de-multiplexing of the optical signals in the upgrade band and the
basic band, and it also meets the above first isolation condition.
All filters used in this embodiment are sideband filters and they
have relatively low cost.
[0097] By changing the filter types and/or their spectral
properties, the embodiment has some variations, for example:
[0098] Variation one: the structure of variation one is still as
shown in FIG. 11 (a), the connection relationship among
f101.about.f104 is unchanged, while the sideband filter f101 is
modified to a band-pass filter with transmission band including
1550 nm.about.1580 nm and reflection band including 1260
nm.about.1500 nm, the sideband filter f103 is modified to a
band-pass filter with transmission band including 1260
nm.about.1280 nm and reflection band including 1290 nm.about.1580
nm; while the sideband filters f102.about.f104 are unmodified.
Obviously, the performance of the modified WDM1 is similar to its
counterpart before the modification. Moreover, it is feasible to
just modify one of f101 and f103 rather than both of them in this
variation.
[0099] Variation two, the structure of variation two is still as
shown in FIG. 11 (a), and the connection relationship among filters
f101.about.f104 unchanged, the spectral properties of the sideband
filters are modified to those shown in FIG. 11 (f).about.(i)
respectively, that is: the transmission band of the sideband filter
f101 includes 1260 nm.about.1280 nm, and the reflection band of the
sideband filter f101 includes 1290 nm.about.1580 nm; the
transmission band of the sideband filter f102 includes 1290
nm.about.1580 nm, and the reflection band of the sideband filter
f102 includes 1260 nm.about.1280 nm; the transmission band of the
sideband filter f103 includes 1550 nm.about.1580 nm, and the
reflection band of the sideband filter f103 includes 1260
nm.about.1500 nm; the transmission band of the sideband filter f104
includes 1260 nm.about.1500 nm, and the reflection band of the
sideband filter f104 comprises 1550 nm.about.1580 nm. In this
variation, WDM1 can also achieve the multiplexing and
de-multiplexing of the optical signals in the upgrade and basic
bands, and it still meets the above first isolation condition.
[0100] Variation three: on the basis of variation two, the sideband
filter f101 is modified to a band-pass filter with transmission
band including 1260 nm.about.1280 nm and reflection band including
1290 nm.about.1580 nm; and/or, the sideband filter f103 can be
modified to a band-pass filter with transmission band including
1550 nm.about.1580 nm and reflection band including 1260
nm.about.1500 nm.
The Eleventh Embodiment
[0101] The structure of WDM1 in this embodiment is as shown in FIG.
12 (a), and WDM1 comprises the band-pass filter f111, the band-pass
filter f112, the sideband filter f113 and the sideband filter f114.
Their spectral properties are respectively shown in FIG. 12
(b).about.12 (e), the transmission band of the band-pass filter
f111 includes 1260 nm.about.1280 nm, and the reflection band of the
band-pass filter f111 includes 1290 nm.about.1580 nm; the
transmission band of the band-pass filter f112 comprises 1550
nm.about.1580 nm, and the reflection band of the band-pass filter
f112 includes 1260 nm.about.1500 nm; the transmission band of the
sideband filter f113 includes 1260 nm.about.1500 nm, and the
reflection band of the sideband filter f113 includes 1550
nm.about.1580 nm; the transmission band of the sideband filter f114
includes 1290 nm.about.1580 nm, and the reflection band of the
sideband filter f114 includes 1260 nm.about.1280 nm.
[0102] In the aspect of the connection relationship, there are
optical channels between the upgrade OLT port of WDM1 and the
common port of the band-pass filter f111, between the transmission
port of f111 and the reflection port of f114, between the
reflection port of f111 and the transmission port (or the common
port) of f112, between the common port (or transmission port) of
f112 and the reflection port of f113, between the transmission port
of f113 and the legacy OLT port, between the common port of f113
and the transmission port of f114, and between the common port of
f114 and the common port of WDM1.
[0103] By modifying the types of the filters and/or the filters'
spectral properties, this embodiment also has some variations, for
example:
[0104] Variation one: the connection relationship among
f111.about.f114 is still as shown in FIG. 12 (a), while the
band-pass filter f111 is modified to an sideband filter with
transmission band including 1260 nm.about.1280 nm and reflection
band including 1290 nm.about.1580 nm; and/or the band-pass filter
f112 is modified to an sideband filter with transmission band
including 1550 nm.about.1580 nm and reflection band including 1260
nm.about.1500 nm. The types and spectral properties of the sideband
filters f113 and f114 are unmodified.
[0105] Variation two: the connection relationship among
f111.about.f114 is still as shown in FIG. 12 (a), f111 is still a
band-pass filter, however, its transmission band includes 1550
nm.about.1580 nm, and its reflection band includes 1260
nm.about.1500 nm; f112 is still a band-pass filter, but its
transmission band includes 1260 nm.about.1280 nm, and its
reflection band includes 1290 nm.about.1580 nm; f113 is still a
band-pass filter, but its transmission band includes 1290
nm.about.1580 nm, and its reflection band includes 1260
nm.about.1280 nm; f114 is still an sideband filter, but its
transmission band includes 1260 nm.about.1500 nm, and its
reflection band includes 1550 nm.about.1580 nm.
[0106] Variation three: on the basis of variation two, the
band-pass filters f111 and/or f112 are modified to sideband
filters, and the transmission or reflection relationship of the
related four bands in the spectral properties of the modified
sideband filters f111 and f112 is the same as that of f111 and f112
in variation two.
[0107] Analyzing the connection relationship and the spectral
property of each filter in the eleventh embodiment and its three
variations, it can be seen that WDM1 in this embodiment and all
variations can achieve the multiplexing and de-multiplexing of the
optical signals in the upgrade and basic bands, and it meets the
above first isolation condition.
[0108] Although various embodiments with different structures are
illustrated above, those skilled in this field can understand that
there may be a lot of other combinations, as long as these
combinations can achieve the wavelength division multiplexing and
de-multiplexing and meet the isolation requirement, they can be
used for WDM1 of the present invention.
[0109] In the following, the G-PON will be taken as an example to
describe the structure of NG-PON compatible with the TDM-PON with
the wavelength division multiplexer provided in the embodiments of
the present invention, as shown FIG. 13.
[0110] The network structure of said NG-PON compatible with the
G-PON comprises the G-PON system network architecture based on the
basic band and the NG-PON system network architecture based on the
upgrade band, wherein, the G-PON system network architecture
comprises the G-PON OLT, the WDM1, the splitter and the G-PON ONU;
the NG-PON system network architecture comprises the NG-PON OLT,
the CATV, the WDM1, the splitter and the NG-PON ONU, wherein, the
WDM1 should be introduced to smoothly upgrade the TDM-PON to the
NG-PON, and the network compatibility is achieved via the
multiplexing and de-multiplexing.
[0111] For the G-PON system, in the downlink direction, the optical
signal whose the central wavelength of downlink wavelength is 1490
nm.+-.10 nm, is transmitted by the Tx optical module at the G-PON
OLT side, and the signal is through Filter 1, and then input via
the legacy OLT port of WDM1, and multiplexed and output by the
common port of WDM1 through the splitter, and sent to the G-PON
ONU, filtered by Filter 3 in the G-PON ONU which matches with the
signal, and finally received by Rx; vice versa in the uplink
direction;
[0112] For the NG-PON system, in the downlink direction, the
optical signal, whose downlink wavelength is 1575 nm.about.1580 nm,
is transmitted by the Tx optical module at the NG-PON OLT side, the
signal is through Filter 2, and combined with a CATV downlink
signal whose wavelength is 1550 nm.about.1560 nm via a WDM device,
and the combined signal (including the downlink signal (whose
wavelength is 1575 nm.about.1580 nm) in the NG-PON and the downlink
signal (1550 nm.about.1560 nm) in CATV) is input via the upgrade
OLT port of WDM1, and then multiplexed and output by the common
port of WDM1, and then sent to the NG-PON ONU via the splitter,
filtered by Filter 4 in the NG-PON ONU which matches with it, and
then received by the Rx. Vice versa in the uplink direction, thus
the case in the uplink direction will not be described here.
[0113] Therefore, for the layout of the G-PON network and the
smooth upgrade of the existing G-PON network, in order to
significantly save the existing ODN network resource, WDM1 must be
introduced to achieve the compatibility of G-PON and NG-PON via the
multiplexing/de-multiplexing function.
[0114] The above description is only the preferred embodiments of
the present invention, and the protection scope of the present
invention is not limited thereto. Any modification and alternative
that is easy to be thought out within the technical scheme
disclosed by the present invention by the persons having ordinary
skill in the art shall all fall into the protection scope of the
present invention. Therefore, the protection scope of the present
invention should be subject to the protection scope of the
claims.
INDUSTRIAL APPLICABILITY
[0115] WDM1 provided by the present invention implements the
wavelength division multiplexing and de-multiplexing of the optical
signals in the basic and upgrade bands. It makes the ODN in the
existing TDM-PON can transport the NG-PON at the same time, so as
to smoothly upgrade the existing TDM-PON to the NG-PON and provide
subsequent network compatibility to the deployed TDM-PON system. In
some embodiments, relatively low cost can still meet the high
isolation requirement of the optical signal in working band by
reasonably using the thin film filters and selecting the spectral
properties of the filters, moreover, the requirements for the
isolation and the optical network insert loss can be overall taken
into account by setting the number of filters and their spectral
properties. A simple but practical technology applied in the
embodiment of the present invention implements WDM1 with low lost
and high reliability; moreover, the system is easy to use and
upgrade.
* * * * *